Among conventional exhaust gas measurement systems, as disclosed in JP-A-Hei11-326161, a system for measuring particulate matters (PM) contained in engine exhaust gas is configured so as to dilute sampled engine exhaust gas with dilution air and lead the diluted exhaust gas to a PM collecting filter to thereby collect PM. Here, a ratio (Q2/Q1) between an engine exhaust gas flow rate Q1 flowing through an exhaust pipe and a sampled engine exhaust gas flow rate Q2 is made constant. And a mass of the PM collected by this filter is obtained by weighing by a precision balance.
Further, among exhaust gas measurement systems, as disclosed in JP-A-Hei8-226879, a constant capacity dilution sampling device (CVS) is configured so that a whole quantity of engine exhaust gas is diluted with dilution air and controlled so as to make a total flow rate obtained by summing up them constant all the time and a part of the diluted engine exhaust gas is sampled in a bag at a constant flow rate. Here, a ratio (Q4/ Q3) between a total flow rate Q3 controlled by the CVS and a diluted exhaust gas Q4 sampled to the bag is made constant. And the diluted engine exhaust gas in the bag is analyzed by a gas analyzer.
Further, among the exhaust gas measurement systems, as disclosed in JP-A 2008-507693, a bag mini-diluter (BMD) is configured so as to sample a part of engine exhaust gas to be diluted with dilution air so as to be a constant dilution ratio so that a part of the diluted engine exhaust gas is sampled to the bag at a flow rate proportional to the flow rate of the engine exhaust gas. Here, a ratio (Q5 / Q1) between an engine exhaust gas flow rate Q1 flowing through an exhaust pipe and a diluted exhaust gas flow rate Q5 sampled to the bag is made constant. And the diluted engine exhaust gas in the bag is analyzed by a gas analyzer.
However, in the case where the exhaust gas measurement system is incorporated with the plurality of measurement instruments, a dilution sampling device dedicated to each of the plurality of measurement instruments is needed, and therefore there is a problem that the exhaust gas measurement system is increased in size. Moreover, due to difference in portions for sampling engine exhaust gas and difference in diluting methods every measurement instrument, properties of exhaust gas introduced to each of the measurement instruments are to be different, and therefore there is a problem that the reliability of the comparison results is bad even though the measurement results of each of the measurement instruments are compared.